Dried Blood Spot Tests for the Diagnosis and Therapeutic Monitoring of HIV and Viral Hepatitis B and C

Abstract

Blood collected and dried on a paper card - dried blood spot (DBS) - knows a growing interest as a sampling method that can be performed outside care facilities by capillary puncture, and transported in a simple and safe manner by mail. The benefits of this method for blood collection and transport has recently led the World Health Organization to recommend DBS for HIV and hepatitis B and C diagnosis. The clinical utility of DBS sampling to improve diagnostics and care of HIV and hepatitis B and C infection in hard to reach populations, key populations and people living in low-income settings was highlighted. Literature about usefulness of DBS specimens in the therapeutic cascade of care - screening, confirmation, quantification of nucleic acids, and resistance genotyping -, was reviewed. DBS samples are suitable for testing antibodies, antigens, or nucleic acids using most laboratory methods. Good sensibility and specificity have been reported for infant HIV diagnosis and diagnosis of hepatitis B and C. The performance of HIV RNA testing on DBS to identified virological failure on antiretroviral therapy is also high but not optimal because of the dilution of dried blood in the elution buffer, reducing the analytical sensitivity, and because of the contamination by intracellular HIV DNA. Standardized protocols are needed for inter-laboratory comparisons, and manufacturers should pursue regulatory approval for in vitro diagnostics using DBS specimens. Despite these limitations, DBS sampling is a clinically relevant tool to improve access to infectious disease diagnosis worldwide.

Keywords: HIV; diagnosis; dried blood spot; hard-to-reach population; hepatitis B; hepatitis C.

FIGURE 1

(A) Possible organization of the diagnosis and management of infections combining rapid diagnostic tests and DBS. The sampling is carried out closer to the person detected or supported. Non-laboratory RDT are carried out in the peripheral structures in parallel with the sending of the DBS to the central laboratory carrying out complementary or confirmation analyses. Results are reported as part of the post-test counseling. (B) Clinical performance of in vitro assays dedicated to HBV, HCV, and HIV infections. The figure is a schematic representation of the clinical performances considered as a trade-off between assay performances and implementation coverage. Diagnosis and monitoring strategies based on different formats of tests have different clinical performances. Each format of test is characterized by its analytical performances mainly estimated by lower limit of detection (LOD), sensibility (Se) and specificity (Sp) based on previously published studies, and its global accessibility depending on parameters such as price, infrastructure requirements, distribution network, and acceptability as evaluated based on our own experience. The clinical performance in a population can be estimate by the proportion of infected persons tested and detected positive. Abs, antibodies; Ag, antigen; HIV Abs, anti-HIV antibodies; HCV Abs, anti-HCV antibodies; IA, immuno-assay; NAT, Nucleic acid tests; Near-POC NAT, Near point of care NAT; RDT, rapid diagnostic test. (C) DBS analyses during the therapeutic cascade for HIV, HBV, and HCV infections. The sampling on DBS allows the realization of the in vitro assays which are necessary at each steps of the therapeutic cascade: screening, confirmation, measurement of the replication, analysis of the therapeutic failures. Recommendations of WHO to the usage of DBS are indicated for each step of the cascade.